Stacking TV Antennas

You’ve probably heard the term antenna stacking, but what does it mean exactly, and is it a good idea? Let’s take a closer look at the concept and see some examples.

“Stacking antennas” means setting up multiple TV antennas, either on the same mast (vertical stacking) or adjacent to each other (horizontal stacking), and combining the received TV signals from these antennas to view the channels from all of them.

This certainly sounds like a great idea. You just buy two or more antennas, point them in different directions, and receive even more channels on your TV.

There are some complexities however. And there are several ways to do it.

To unpack all this, let me first illustrate the concept by describing the most common scenario of antenna stacking: getting signals from different directions.

You might have a Yagi-style antenna on your roof right now that’s pointed at a group of towers, say to the north.

Outdoor Yagi antennas like this one are great for picking up distant stations but typically have a reception beam width that’s narrower than 90 degrees (and many times, much narrower).

On your TVFool.com signal report, you might’ve noticed other groups of stations in different directions, but alas, you’d need either a multidirectional antenna or a second unidirectional antenna like another Yagi to get those.

In the end, you might decide to mount a second unidirectional antenna to pick up the other group of stations, and combine the signals from both antennas. That’s what stacking is.

3 Reasons Why People Stack TV Antennas

Technically speaking, TV antennas can be combined in myriad ways for to achieve different scenarios.

For instance, they can be vertically or horizontally stacked; you can amplify one or both antennas; you can aim them in different directions or in the same direction.

Despite these different configurations, there are three common scenarios in which consumers stack antennas:

A. They’re trying to receive TV signals from stations outside of their current antenna’s reception angle.

B. They’re trying to receive on another frequency band (e.g., trying to get a high VHF signal broadcast by a particular station if their existing antenna is UHF only).

C. They want to increase their total antenna gain in the hope of upping their signal quality and maybe even get another channel or two (by aiming both in the same direction).

Most people add extra antennas for achieving scenarios A and B above.

Admittedly, some are also trying increase their total antenna gain (C). This involves some technical challenges — such as understanding horizontal and vertical signal polarization, estimating the size and shape of both antennas’ reception capture areas, etc. — and can bring mixed success.

If you want to increase your antenna gain, it may easier and less complex to simply get a higher-gain antenna with a wider reception beam (with possibly a preamplifier), rather than trying to combine two smaller ones.

In fact, high-gain, multidirectional antennas like the Antennas Direct DB8e HDTV Antenna are more like stacked antennas.In this article, I’ll be focusing on the more common scenarios of antenna stacking (i.e., receiving signals from another direction or on another frequency band).

Most people attempt to stack a maximum of two antennas (rather than say, three or four), so that’ll be my base case.

Video: Facts About Antenna Stacking

Ways to Stack TV Antennas

Let’s first look at some special considerations for antenna stacking, before learning how to mount them.

Should You Stack TV Antennas Vertically or Horizontally?

Does it make a difference whether you install your second antenna on top of the other on the same mast, or place them side by side?

Personally, I’d first try a vertical arrangement of antennas on the same mast (if possible), before trying with a horizontal placement; that is, placing the second antenna nearby or on the other side of the roof or attic.

However, many people also succeed with horizontal stacking. It really comes down to your local situation — yes, TV signals are horizontally polarized but there are other factors to consider.

For example, perhaps your signals are coming through a nearby forest, causing interference.

You may find that placing the second antenna in another area of your home gets better results.

So, the jury’s out when it comes to generalized answers regarding vertical vs. horizontal stacking.

But at the very least you should ensure they’re both sufficiently separated to minimize interference between them.

Separating Antennas to Minimize Interference

Although they’re passive receptors, antennas generate a subtle electrical field that can interfere with the reception of another antenna placed too close.

They need to be separated by a certain distance corresponding to the size of the UHF or VHF wavelengths they’re capturing.

This comes out to around 1/4th of the size of the wavelengths they’re receiving.

Now, each individual frequency within the UHF and VHF bands has a unique wavelength size, so when calculating the separation it’s useful to think in terms of the maximum wavelength size your antennas will receive.

The maximum wavelength of a UHF signal can be over two feet, while VHF wavelengths can span over six feet in length.

In fact, various elements on an antenna (like dipoles, reflectors, etc.) are proportionately sized in relation to these wavelengths to precisely capture radio waves.

It’s best practice to keep around 2 – 4 feet of separation between any two stacked antennas (whether UHF or VHF antennas).

Although one might think you should mount a VHF antenna even farther away (because of its wavelength), in general the interference caused by both antennas probably won’t be substantial enough to affect your signal.

But it’s still a good idea to not mount them too close to each other.

Here of course I’ve mentioned a minimum distance. You can mount your antennas even farther away, putting more distance between them to further reduce potential interference.

What You’ll Need

There are some factors to consider when stacking antennas.

I’m summarizing them here but will go into greater detail below:

Which type of second antenna should you get?

When combining the signals from both antennas, should you use a diplexer or signal combiner? This will depend on whether you’re trying to achieve scenario A or B above

Antenna coaxial cable — these should be of the same length and type for both antennas!

Whether you want to amplify your antenna line or not

If you’re vertically stacking your antennas on the same mast, your configuration might look similar to the diagram below.

Vertically stacked antennas on the same mast

Acquiring the Second Antenna

When starting your project, you’ll either have an extra antenna on hand, or you’ll need to buy it.

If you’re stacking antennas to get stations in other directions or on another frequency band, there are no special considerations for choosing the second antenna (other than that it can actually pick up the other stations).

For instance, if you have a UHF-only antenna and you want a second antenna to get that public channel that’s broadcast on high VHF, then read the fine print of the antenna to ensure it can actually pick up those frequencies (RF channels 7 – 13 in this case).

Let’s now look at the type of signal combiner you should get for both antennas.

The type you’ll get will depend heavily on whether you’re stacking antennas to get different frequencies (scenario B) or just to get channels from another direction (scenario A).

Combining Signals: Diplexer

A diplexer is a device that receives separate feeds and combines these into one signal in a more sophisticated way than a normal signal combiner would (see below).

For instance, a diplexer might take into account the signals’ frequencies and apply multiplexing.

Diplexers are prevalent in the world of satellite TV. They’re less common in the OTA consumer market however.

So why would you need a diplexer for your TV antennas?

You’ll need it for combining signals from antennas with different frequency bands (UHF with VHF — or scenario B above).

It takes signals from one UHF-only antenna and combines these with signals from a VHF-only antenna.

You mount this device directly on the antenna mast — between the antennas to help ensure the antennas’ coaxial cable lengths are equal. The diplexer box is actually inside the black waterproof case you see in the image.

After mounting your antennas, you’ll attach their coaxial cables to this device, by plugging them underneath in the two IN ports. The device has an OUT port for running a coaxial to your splitter, TV, or converter box.

As with many diplexers for the OTA consumer market, this one operates passively so it doesn’t come with an AC power supply.

Also, you should use it for its stated purpose: combining a UHF with a VHF antenna.

If you try another combination, say, two UHF antennas, the device won’t allow the UHF signals to pass through the VHF port.

Combining Signals: Signal Combiner or Coupler

Another type of device is an ordinary signal combiner (also called a signal coupler).

It’s generally a simpler device than a diplexer, in that it “indiscriminately” combines signals from two antennas receiving from any frequency band.

In this way, it acts more like a reversed splitter — with the two ports normally going out to the TVs now acting as inputs for the antennas.

You use a signal combiner or coupler for scenario A above.

You can connect any type of antenna band to any of the inputs. For example, you can connect a coaxial from a UHF/VHF antenna into one port, then a UHF antenna into the other.

A Word on Signal Loss

Basically, all devices and cables you’re using will introduce some (fractional) amount of loss, potentially degrading your TV signal.

In that article, I advised getting a splitter with the exact number of output ports matching the number of TVs you plan on hooking up.

That way you don’t experience unnecessary signal loss, as unused device ports still cause losses.

The same principle applies to diplexers and signal combiners. You should avoid buying a device whose number of IN ports exceeds the number of antennas you’re joining.

Antenna Coaxial Cable

While stacking antennas works most of the time, some customers are nevertheless unable to get their combined antennas to work properly.

I suspect some of this has to do with phase problems.

Let’s visualize this for a moment. TV signals propagate outwards from transmission towers as waves that oscillate up and down, and once received by an antenna, these signals continue travelling down the coaxial cable to the combiner device.

When multiple antennas receive signals, it’s important the signals arrive at the combiner at the same time.

When this is the case, they arrive in phase with each other. If they arrive at (even slightly) different times, they’re out of phase.

Two TV antennas receiving out of phase signals from different sources

Signals arriving out of phase resemble multiple waves overlaid on one another whose peaks and troughs aren’t in sync, thereby weakening or even cancelling each other out.

It’s therefore essential to connect the antennas to the combiner device with coaxial cables that are of the same type and length.

Even if you mount one antenna a distance further away from the combiner device than the other, you should still use the same length of cable for both antennas, coiling the cable of the closest antenna if necessary.

(This cable has excellent characteristics for TV but note that its length is 50 feet — your combiner will likely be closer to your antennas than that. If you buy this cable you’ll need crimping tools to cut off the proper lengths. Amazon offers its own branded tri-shielded coaxial cable that comes in shorter lengths, the smallest of which is 4 feet long.)

Using an Amplifier with a Signal Combiner

In some situations you may want to attach an amplifier device (a preamplifier or distribution amplifier) somewhere along the line in order to boost your TV signal.

The diagram below shows a typical setup with vertically stacked antennas using a preamplifier device attached to the mast:

Vertically stacked antennas on the same mast

The trick here is knowing whether your diplexer or signal combiner allows “pass-through” of electric current on the coaxial cable that’s amplified.

By default, splitters and signal combiners are designed to stop surges travelling up the line from your TV (if it’s faulty, for instance) to the antenna.

However, many of them will have one clearly labeled IN port that allows you to attach an amplified coaxial cable.

This means: make sure the combiner device you’re purchasing allows pass-through of current if you intend on adding an amplifier to the line.

If you’re vertically stacking the antennas and need a taller mast, keep in mind that the diameter of the new mast may differ slightly, and possibly be too wide for the mounting brackets you’re currently using for the first antenna.

Make sure you have all the necessary parts before starting.

If you’re installing the antennas yourself, you should consider asking one or two people to help out. They can assist with testing or with moving the antenna and observing the quality of signal on the TV to speed up the steps.

IMPORTANT: Safety should be your number one priority when installing an outdoor TV antenna – especially on your roof.

Step 1: Find the Best Place to Set Up the Second Antenna

As I mentioned earlier, you’ll need the appropriate antenna to pick up the extra stations you want.

Finding the best antenna for your needs is an extensive topic I’ve covered here, but suffice it to say it’s best to verify the second antenna will get the stations on its own before you join both together.

To that end, you’ll also need to pick an appropriate place, which goes back to the earlier discussion in this article on whether you should vertically or horizontally stack the antennas.

Your main criteria should be choosing a place that offers signal strength that will be sufficient for overcoming any loss you’ll encounter from the signal combiner and the rest of your setup.

Personally, I always try simply mounting the second antenna on the same mast as the first (it’s in the same spot that’s optimal for the first antenna after all) but you may find this doesn’t deliver the needed signal quality in your situation.

Step 4: Attach Both Antenna Coaxials to the Signal Combiner

Install the diplexer or signal combiner to the mast or whichever place is relatively central with respect to both antennas.

Remove the cable you previously lead from the second antenna to your TV in the last step, and attach the coaxial cables from each of the antennas to the respective IN ports of the combiner device.

If one of the antennas has a preamplifier, take care that you’re attaching that antenna’s coaxial to the correct IN port with “power pass-through” indicated.

As mentioned earlier in this article, ensure that both antenna coaxials are of equal length and type, otherwise you may get phase problems such as multipath interference (ghosting).

Step 5: Run a Coaxial Cable from the Signal Combiner to Your TV

At this stage, you know that both antennas are functioning correctly (independently) and you’re now basically setting up the rest of the reception system, including any amplifiers and splitters along the way.

Connect the coaxial cable from the combiner’s OUT port to your TV or converter box. The digital tuner on your TV or converter box should be getting the combined signals from both antennas.

Turn on your television and run a channel scan. The channels you receive should correspond to the signal report you might’ve gotten for your location from TVFool.com or DTV/maps.

Check also the signal strength of each channel to make sure they’re strong to begin with.

If you’re not getting the full list of channels you’re expecting, you might have to diagnose the issue and make changes.

Amplifiers (either a preamplifier or distribution amplifier) are known to sometimes cause issues with signal combiners as they may add too much noise to the line.

If you’re using an amp, I’d suggest you unplug it and rescan your channels as a first troubleshooting step.

Step 6: Ground the Second Antenna and Weatherproof Parts

Once everything’s working correctly and you’re satisfied with reception, make sure to check that the antenna parts, coaxial cable connections, etc., are sufficiently weatherproofed.

Not taking this step can cause the equipment to corrode and degrade at a faster rate than otherwise, affecting your TV reception.

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